Aortic valve replacement with cryopreserved aortic allograft: ten-year experience

OBJECTIVE: Cryopreserved aortic allograft can be used for aortic valve replacement in congenital, rheumatic, degenerative, and infected native valve conditions, as well as failed prosthetic valves. This study was conducted to determine the long-term results of aortic valve replacement with cryopreserved aortic allografts. METHODS: Aortic valve replacement with cryopreserved aortic allografts was performed in 117 patients from July 1985 until August 1996. All patients requiring aortic valve replacement regardless of valve disease were considered for allograft replacement; the valve was preferentially used in patients under age 55 years and in the setting of bacterial endocarditis. Four operative techniques involving cryopreserved aortic allografts were used: freehand aortic valve replacement with 120-degree rotation, freehand aortic valve replacement with intact noncoronary sinus, aortic root enlargement with intact noncoronary sinus, and total aortic root replacement. Valve function was assessed by echocardiography during the operation in 78 patients (66%) and after the operation in 77 patients (65%). RESULTS: One-hundred eighteen aortic valve replacements with cryopreserved aortic allografts were performed on 117 patients; mean age was 45.6 years (range 15 to 83 years) and mean follow-up was 4.6 years (range up to 11 years). Intraoperative echocardiography disclosed no significant aortic valve incompetence. There were four operative deaths (3%) and seven late deaths; freedom from valve-related mortality at 10 years was 9:3% +/- 4.55%. New York Heart Association functional status at latest follow-up was normal in 98 (94%) patients. On postoperative echocardiography, 90% had no or trivial aortic valve incompetence. Freedom from thromboembolism at 10 years was 100% and from endocarditis, 98% +/- 2.47%. Seven (6%) patients required valve explantation, four for structural deterioration. At 10 years, freedom from reoperation for allograft-related causes was 92% +/- 3.47%. CONCLUSIONS: Aortic valve replacement with cryopreserved aortic allografts can be performed with low perioperative and long-term mortality. Most patients have excellent functional status, and reoperation for valve-related causes is unusual. Aortic valve replacement with cryopreserved aortic allografts demonstrates excellent freedom from thromboembolism, endocarditis, and progressive valve incompetence.     

Preoperative chemoradiation and pancreaticoduodenectomy for adenocarcinoma of the pancreas

The goal of multimodality therapy for localized pancreatic cancer is to maximize local-regional disease control and patient survival. In contrast to surgery for other solid tumors, prolonged recovery following pancreaticoduodenectomy may prevent the timely delivery of postoperative adjuvant therapy. Therefore, efforts at The University of Texas, M.D. Anderson Cancer Center have focused on the delivery of chemotherapy and radiation therapy prior to surgery in patients with localized pancreatic cancer. Clinical trials have emphasized the use of altered-fractionation schedules of radiation therapy combined with novel radiation-sensitizing agents. All treatment schemes aim to decrease toxicity and treatment time while improving therapeutic efficacy.     

Alpha interferons--new therapeutic modalities

Interferons are naturally occurring substances. In fact, interferons are intercellular signalling proteins produced by cells in response to various biological and synthetic stimuli. Three major classes of interferons have been identified: interferons alpha, beta and gamma. Interferons originate from natural sources and are products of recombinant technology. Two forms of recombinant alpha-interferons, 2a and 2b, are available. Alpha-interferons are secreted and synthetised by leucocytes and lymphoblasts. The objective herein is to review the current therapeutic implications of alpha-interferons. Interferons alpha have antiviral, anticancer and immunomodulatory activities. Clinical trials have proved interferons alpha to be of special value as adjuvant therapy (first line drugs) for hairy cell leukemia, virus hepatitis B and C and condylomata acuminata. The efficacy of interferons alpha is now also being evaluated in other malignancies and virus diseases. For instance, interferons alpha are an important advanced modality in the management of chronic myelogenous leukemia and can be considered a first-line therapy option in patients who cannot receive or relapse following allogenic bone marrow transplant. Of course, further research is also required to evaluate combination therapies with interferons alpha and other agents. Presently malignancies have the broadest potential in application of interferons alpha therapy. Hairy cell leukemia responds to interferons alpha in up to 90% of patients, Kaposi's sarcoma, which occurs primarily in association with AIDS, benefit in up to 40% of patents, lymphomas respond in about 65% of patients whereas chronic myelogeneous leukemia in more than 80% of patients in early cases. The uses of interferons alpha in infectious diseases (condylomaty acuminata, rhinovirus infection, protozoal, parasitic and fungal intracellular infections) may also be significant. However, the cost of interferons alpha is too high. This makes interferons alpha a second line therapy, but not in patients where it is more effective than alternative treatment. Interferons alpha are cytokines (intercellular signalling proteins) which have antiviral, anticancer and immunomodulatory activities. Interferons alpha therapy represents an important advanced modality in the management of patients with hematological diseases, malignancies, lymphomas, solid malignant tumours and viral infections. Clinical trials have proved interferons alpha to be of special value as first line drugs for hairy cell leukemia, virus hepatitis B and C and condylomata accuminata. Interferons alpha are used as single primary therapy, adjuvant therapy and maintenance therapy. The limiting factor for the application of interferons alpha is the cost of treatment.     

Thapsigargin and receptor-mediated activation of Drosophila TRPL channels stably expressed in a Drosophila S2 cell line

The Drosophila melanogaster genes, transient receptor potential (trp) and transient receptor potential-like (trpl) encode putative plasma membrane cation channels TRP and TRPL, respectively. We have stably co-expressed Drosophila TRPL with a Drosophila muscarinic acetylcholine receptor (DM1) in a Drosophila cell line (S2 cells). Basal Ca2+ levels measured using Fura-2/AM in unstimulated S2-DM1-TRPL cells were low and indistinguishable from untransfected cells, indicating that the TRPL channels were not constitutively active in this expression system. Activation of DM1 receptor in S2-DM1-TRPL cells by 100 microM carbamylcholine induced Ca2+ release from an intracellular Ca2+ pool followed by a Gd(3+)-insensitive Ca2+ influx. Pretreatment of S2-DM1-TRPL cells with 10 microM atropine abolished Gd(3+)-insensitive Ca2+ influx triggered by carbamylcholine, but the response was not blocked by prior incubation with pertussis toxin. TRPL channels could also be reliably activated by bath application of 1 microM thapsigargin for 10 min or 100 nM thapsigargin for 60 min in Ca(2+)-free solution. In some cells, TRPL channels activated by thapsigargin could further be activated by carbamylcholine. The findings suggest that, when stably expressed in the S2 cell line, TRPL may be regulated by two distinct mechanisms: (i) store depletion; and (ii) stimulation of DM1 receptor via pertussis-toxin insensitive G-protein (or the subsequent activation of PLC), but without further requirement for Ca2+ release.     

Reproducibility of fluorine-18-6-fluorodopa positron emission tomography in normal human subjects

We calculated the mean energy required to produce an ion pair (W) in methane-, propane- and butane-based tissue-equivalent (TE) gas mixtures from W values in pure constituent gases according to various models for energy partition among gas components. We found an agreement between the experimental and calculated W values in the methane-based TE gas regardless of the model concept. In contrast, only those models which take into account differences in the stopping powers, total ionization cross sections and model constants of gas components give acceptable results for the propane-based TE gas. The calculated W value for high-energy electrons in the isobutane-based TE gas mixture is 25.2 eV for high-energy electrons and 28.0 eV for approximately 5 MeV alpha particles.     

Dynamische Belastungen von Zyklonabscheidern bei Anwendung in Blowdown-Systemen

Transient Loading of Cyclone Separators on Use in Blowdown Systems. On use of cyclone separators for phase separation in blowdown systems, pressure-discharge systems, and flaring units, considerable momentary liquid forces are often encountered. Only few details are known about the transient loading and dimensioning of such systems. Thus the behaviour of the entering surge of liquid and its effect on cyclone separators has now been studied experimentally and theoretically. Water/glycerol mixtures of various viscosities were used in these model experiments. After entering the separator the liquid immediately forms a compact wall film. It rapidly expands sideways under the action of the centrifugal force and simultaneously decelerates. A two-dimensional planar mathematical model serves for stepwise calculation of the experimental results with regard to film extension, deceleration, and the resulting transient forces. The results are summarised in the form of design criteria.     

Pathogenicity of human anti-platelet factor 4 (PF4)/heparin in vivo: generation of mouse anti-PF4/heparin and induction of thrombocytopenia by heparin

Acinetobacter baumannii strain A148, a clinical isolate resistant to imipenem (MIC = 32 mg l-1), synthesized two beta-lactamases with pIs 6.3 and > 9.2. The pI 6.3 enzyme hydrolyzed the penicillins, including isoxazoylpenicillins, first-, second- and, to a lesser extent, third-generation cephalosporins. It was inhibited by chloride ions and by the penem beta-lactamase inhibitor BRL 42715. Clavulanate was a weak inhibitor and EDTA did not affect the beta-lactamase activity. This enzyme also hydrolyzed imipenem with a catalytic efficiency (Kcat/Km) of 1500 mM-1 s-1. Moreover, this purified beta-lactamase produced a positive microbiological clover-leaf test with imipenem. Therefore, the pI 6.3 beta-lactamase was considered to be involved in the imipenem resistance of A. baumannii strain A148.